This is part of a Big Leaf Maple, they grow 80' tall, and spread out a good 30-50' at top. That means a lot of leaves. In this case, Kubota Gardens has nicely pruned off excess branches to keep it fairly stable. The Big Leaf Maple has a deep root system that ensures it doesn't fall over easily in heavy winds, but the branches break. The root system is part of the reason it is difficult to garden underneath them. To read more about how to do so, this article has good links and practical experience.
